Z64 



THE QUARTERLY REVIEW OF BIOLOGY 



tion. There are at this time some inter- 

 stitial cells, but they are not abundant. 

 He found them abundant during the 

 summer. Ganfini (17) repeated and ex- 

 tended the work on marmots. He found 

 the interstitial cells as abundant in winter 

 as in the sexually active season. He 

 stated that they were more nearly round in 

 winter and appeared to be secreting less 

 actively. 



Rasmussen (30) made a complete study 

 of hibernation effects upon the testis in 

 Marmota monax. From his data it seems 

 that spermatogenesis progresses slowly 

 during the late fall and winter months. 

 In early March the spermatogenic activity 

 increases markedly and reaches its height 



Regaud (31), Lecaillon (2.5), and 

 Tandler and Grosz (34) have made a com- 

 prehensive study of the seasonal changes in 

 the testis of the mole (Talpa europea). 

 From their work it is evident that 

 spermatogenesis proceeds in autumn and 

 winter. The spermatogenic activity in- 

 creases during late February and attains 

 its height during March . At this time the 

 testis is three times its usual diameter, and 

 this increase results entirely from increase 

 in germ cells. Rutting is during March, 

 and by the end of the month most of the 

 sperm are gone and the testis again de- 

 creases in size. Thereafter it reaches a 

 low ebb in July, when only a syncytium 

 of Sertoli cells and a few spermatogonia 



MAR. APR MAY JUNE JULY AUG-. SEPT. OCT. NOV. DEC. 



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CHART "VT MARMOTA MONAX 



- QUANTITY OF .SPERMATIC TISSUE, 



during the latter part of March and the 

 first part of April. Thereafter sperma- 

 togenesis quickly subsides, and in June 

 and July it is at its lowest point. From 

 September on it again progresses slowly. 



Interstitial cell hypertrophy starts just 

 before mating, and the cells reach their 

 maximum development after spermato- 

 genesis has ceased and the tubules are 

 empty. They remain well developed until 

 July, at least two months after the cessa- 

 tion of the spermatogenic cycle. The 

 mating season is during late March and 

 early April, and young are bom during 

 the first part of May. Mating thus fol- 

 lows the great wave of spermatogenesis 

 and precedes the crest of interstitial cell 

 hypertrophy. See chart VI. 



• QUANTITY or INTERSTITIAL TISSUE 



remain in the tubules. The interstitial 

 cells are minimal during February and 

 March. They increase immediately after 

 mating, when the sperm are gone. When 

 spermatogenesis again takes place in the 

 fall the interstitial cells decrease, though 

 they are still numerous during the winter 

 according to Lecaillon. 



In moles it is quite evident that inter- 

 stitial cell hypertrophy occurs when 

 spermatogenesis is minimal and the 

 tubules empty. It does not precede 

 mating but follows it. This is clearly 

 shown in chart VII herewith presented. 



According to Marshall (z6) testes of 

 the Hedgehog (Erinaceus europeus) begin 

 to increase in size about the end of March, 

 and by the middle of April they are 



